- to support "old-style" gear/flap control (operation as long as button
pressed/lever pushed -> b29/hurricane), let bindings not only report
up/down, but up (-1), stop (0), down (1).
- let controls.flapsDown() ignore "stop" so as to remain compatible with
prior behavior
- adapt all joysticks/aircraft (sigh)
- some minor cosmetics in joystick configs, such as indentation fixes
controls in the cockpit vs. which wheels they apply to. FlightGear now
sets /controls/gear/brake-left, /controls/gear/brake-right, and
/controls/gear/brake-parking. It should be up to the FDM to sort out
which wheels under which circumstances are affected by these controls
and ultimately what happens to the physical motion of the aircraft.